JPS6097315A - Display device - Google Patents

Abstract

PURPOSE:To eliminate the need for an analyzer and to obtain a bright display image by the constitution in which the ray past a polarization control element is made incident on a light transmittable mirror by controlling the voltage to be impressed at an incident angle of about the angle of polarization and the reflected light thereof is conducted to an eye range. CONSTITUTION:The ray from a light source 1 passes through a polarizer 2 by which the ray is polarized to linearly polarized light oscillating in an X-axis direction. The polarized light passes through a liquid crystal cell 3 and is made incident on a light transmittable mirror 6 at an incident angle theta of about angle theta0 of polarization. The reflected light thereof is conducted to an eye range 7, i.e., the eye's position by which a display image 8 is obtd. The polarizing component oscillating in the X-axis direction, i.e., the S component performs switching or modulation of the transmitted light at the mirror 6 by the control of the voltage to be impressed to the cell 3 as the incident angle to the face of the mirror 6 is installed at the angle theta0. The bright display is obtd. when the cell 3 is on.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a display device, and particularly to a head-up display device comprising a combination of a polarization control element such as a liquid crystal display element and a light-transmitting mirror.

[Prior art]

Conventionally, there has been a device of this type as shown in FIG.

FIG. 1 is a block diagram showing a conventional liquid crystal display device.

In the figure, (1) is a light source, (2) is a polarizer, and (3) is a polarization control element that changes the polarization state of passing light depending on the applied voltage value. In this case, a liquid crystal display element is used. A pair of transparent plates (3a) (3e) and these transparent plates 9
-1 plate (3a) (3e) and the nematic liquid crystal thin film (3c) arranged in a twisted orientation between the transparent plate (3a)
) It consists of a liquid crystal cell enclosing transparent conductive electrodes (3b) and (3a) respectively disposed on the inner surface of (3e). (4
) Vi analyzer, (5) I″i with a control circuit that controls the voltage value applied to the liquid crystal cell (3).
) (3a).

In addition to such transmissive type liquid crystal display devices, there are
A reflective type in which a reflector is placed at the light source (1) and illumination light such as external light or source light is applied from the analyzer (4) side, or the reflector is translucent. A compromise between transmission and reflection has been proposed.

Now, in the mode of using illumination light from the back (transmission) of a transmission type or a combination of transmission and reflection type, the light rays emitted from the light source (1) are transmitted either directly or through a translucent reflector. After passing through, it passes through a polarizer (2) and becomes linearly polarized light. Next, the polarization state of the linearly polarized light changes depending on the magnitude of the voltage applied to the nematic liquid crystal thin film (3c) after passing through the liquid crystal cell (:().Next, the light beam changes depending on its polarization state. Therefore, only the polarized light components allowed by the analyzer (4) pass through.

In the external light utilization (reflection) mode of a reflective type or a hybrid transmission/reflection type, illumination light such as external light enters from the analyzer (4) side and passes through the analyzer (4). The light beam becomes linearly polarized. Next, the linearly polarized light passes through a liquid crystal cell (3), and the polarization state of the linearly polarized light changes depending on the magnitude of the voltage applied to the nematic liquid crystal thin film (3c). Next, the light beam passes through a polarizer (2), and only the polarized component that is r

Next, the light is reflected by a reflective plate or a translucent reflective plate placed in parallel with the polarizer (2). Then the light beam is again polarized (2
), the liquid crystal cell (3), and the analyzer (4). Other suitable voltages are nematic liquid crystal thin film (3c)
If K is added, different amounts of rays will pass through.

Needless to say, in a transmissive/reflective hybrid type, both the transmissive type and the reflective type work together.

Using this type of translucent, reflective, or hybrid type liquid crystal display element, the light emitted from the liquid crystal display element is reflected obliquely by a translucent mirror, and the display pattern is superimposed on the scenery through the translucent mirror. A display device that can be mounted on a display device, that is, a liquid crystal head amplifier/display device, has been proposed.

However, the illumination light has more light attenuation layers (Di
d photons (2), analyzers (4), transmissive mirrors, etc.), so in the case of transmission type or transmission mode, the light source must be relatively stiff to obtain the desired brightness. It was necessary to make it bigger. K, who loves Kohi,
It was necessary to increase the input power, which was a problem from the perspective of energy conservation. Furthermore, when the input power is increased, the heat generated by the light source increases, and there is a problem in that the margin of the first working area of the system decreases. For the same reason, the reflection type or reflection mode was flooded with external light, so it was not put into practical use.

[Summary of the invention]

This IJ1. J was created to eliminate the drawbacks of the conventional ones as described above, and includes a polarization control element in which the polarization state of the passing light ray changes depending on the applied voltage value, and a voltage applied to this polarization control element is controlled. The object of the present invention is to provide a control circuit for controlling polarization, and a display device in which a light beam passing through a polarization control element is made into an eave and a translucent mirror that directs the reflected light to an eye range when the light beam is incident at an incident angle approximately equal to the polarization angle. There is.

[Example of departure j]

Below is this message! One embodiment of 114 will be described with reference to the figures. FIG. 2 is a configuration diagram showing a transmission type head-up liquid crystal display device according to an embodiment of the present invention. In the figure (2)
is a R11) photon that converts the light beam from the light source (1) into linearly polarized light in the X direction as shown in the figure. (6) In the I/i translucent mirror, the polarization control element (in this case, a liquid crystal display element or liquid crystal cell) (3) and the translucent mirror (6) are connected to the light source (1).
A part of the light beam emitted from the liquid crystal cell (
3) and enters the translucent mirror (6) at an incident angle θ with a polarization angle of approximately θO, and the reflected light enters the eye range (
7), that is, it is arranged so as to reach the eye position. (8
) is the displayed image. The translucent mirror (6) is obtained by coating the surface of a transparent substrate, such as a glass plate, with a material having an appropriate refractive index, an appropriate thickness, and an appropriate number of layers to obtain arbitrary reflection characteristics. The polarization angle θO and reflectance R are obtained by thinly depositing aluminum on a glass plate. FIG. 3 is a curve diagram showing the incidence angle dependence of the reflectance of a translucent mirror with respect to polarized light according to an example of this invention. In the figure, RpFi
The reflectance Rs for polarized light whose electric field oscillates parallel to the plane of incidence (referred to as the P component) is also perpendicular (referred to as the S component). θ0 is the polarization angle of 1. The angle of incidence at which Rp is 0,
That is, the angle of incidence is such that the light reflected from the surface of the translucent mirror (6) becomes completely linearly polarized light.

With such a configuration, the light ray leaving the light source (1) is
The light passes through the polarizer (2) and becomes linearly polarized light that vibrates in the X-axis direction. Next, it passes through the liquid crystal cell (3) and the liquid crystal thin film (3c
) The polarization state changes depending on the magnitude of the voltage applied to the liquid crystal cell (3), so to speak.

For example, if the liquid crystal cell (3) is of the twisted orientation (TN) type, when a voltage exceeding the dark value is applied, it becomes linearly polarized light that vibrates in the X-axis direction, and when no voltage is applied, it vibrates in the Y-axis direction. It becomes linearly polarized light.

In other words, 1 is incident on the transparent mirror (6) due to the voltage.
1+i! The S and P components of the light are switched between each other. In other words, the ratio of both components can be changed depending on the degree of applied voltage. Here, a case where such a TN type liquid crystal cell is used will be exemplified.

Now, in the translucent mirror (6), the polarized light component vibrating in the X-axis direction, that is, the S component, is relatively The P component of the polarized light component that is reflected with a large reflectance Re and vibrates in the Y-axis direction is reflected with a relatively sufficiently small reflectance Rp, and reaches the eye range (7).

Here, ignoring minute reflections and absorption, the brightness of the light source (1) is Bl, and the transmittance of the polarizer (2) to natural light is Tp.
, if the transmittance of the liquid crystal cell (3) is Tlc, then the brightness Bt of the display is as follows: When voltage is applied to the liquid crystal cell (3), that is, when it is ON, Bt=RsXT:LcXTpXB1 With no voltage When added, that is, when it is OFF, Bt=Rp
XTlcXTpXB1.

Here, as is clear from FIG. 3, R8>
Therefore, according to this embodiment, switching or modulation of transmitted light can be achieved by controlling the voltage applied to the liquid crystal cell (3). Therefore, if at least one of the transparent J conductive conductors tfi (3b) and (3a) is divided into multiple flA regions and a full voltage is applied to each display unit formed, the light will be emitted for each display unit. is switched, so that a display pattern consisting of an arbitrary combination of bright and dark parts is formed.

Here, the conventional transparent type display IJ, JrusaBtj
Similarly, since this device has an extra analyzer, if the polarized light transmission axis direction of the analyzer (4) is parallel to the polarized light transmission axis direction of the polarizer (2), the polarized light transmission axis The transmittance of the analyzer for AIIL light vibrating in the direction and in the direction perpendicular to this is multiplied by the above formula BtlCTap or Tac, respectively, so when the liquid crystal cell (3) is ON, Bt 'j=RaX:1' When apXT1cXTpXB1 is OFF, Bt j=RpXTaaXTlcXTpxBl.

These things could be easily confirmed through experiments.

In other words, in the above embodiment of the present invention, when the liquid crystal cell (3) is turned on, 1 /
It is important to be able to achieve a display that is twice as bright as Tap.
It became 1 rak.

FIG. 4 is a configuration diagram showing a reflective head-up liquid crystal display device according to another embodiment of this J. In the figure,
(9) is a reflecting plate made of aluminum or the like. In this case, if the brightness of the external light is Be, the external light Be passes through the liquid crystal cell (3), passes through the polarizer (2), becomes linearly polarized light, is reflected by the reflector (9), and is reflected again. , the polarizer (2) enters and passes through the linearly polarized light, passes through the liquid crystal cell (3) again, and then passes through the transparent mirror (6) in the same manner as in the above embodiment. ) and reaches the eye range (7). Therefore, the reflectance of the reflection 4fi (9) is Rr, and the polarizer (2) for polarized light vibrating along the polarized light transmission axis direction.
If the transmittance of is Tpp, then the brightness of such a display is B
When rVi is ON, Br=RsXT ppXRrXTp
When XTlc2XBeOFF, Br=RpXTppXRrXTpXT1cXBe.

Expressing the display brightness Brj of a conventional reflective type in the same way as above, since this type has an extra analyzer (4), the transmittance of the analyzer for natural light is expressed as Ta.
, where Tpc is the transmittance of the polarizer (2) for polarized light vibrating in a direction perpendicular to the direction of the polarized light transmission axis, and the equation for Ei14 of the reflective type described above is multiplied by Ta and Tap or Tac. becomes. Therefore, when ON, Brj=RsXTapXRrXTpp2XT1c2XT
When aXBeOF E', Br j=11pXTacXTppXRrXTpcXT
1c2XTaXBe.

These seven facts were easily confirmed by experiment.

In other words, compared to the conventional reflective type, when the liquid crystal cell (3) is 0, the device of this invention has a
p) It has become clear that it is possible to realize twice the brightness of the display.

FIG. 5 is a block diagram showing a transmissive/reflective head-up liquid crystal display device according to another embodiment of the present invention. (10
) is a translucent reflecting plate installed between the light source (1) and the polarizer (2). This translucent reflector (1o) has a surface that is uneven on the scale of the wavelength of light, so that when light is reflected, the light is diffused but the polarization state is maintained as much as possible. be done. Furthermore, it should have as little light absorption as possible, and either reflect or transmit light. For example, such a substrate is made by depositing a material having a higher refractive index, such as zinc sulfide, on a transparent glass substrate with an uneven surface to a thickness comparable to the wavelength of light. For example, a commercial product (manufactured by Nitto Denko Corporation) NPF-
It is said to be something like Q-42.

In such an apparatus, a light beam originating from a light source (1) passes through a translucent reflector (1o) and then reaches an eye range (7) in the same manner as in the above-mentioned transmissive type. The contribution of the light source (1) Bdt to the display brightness is the difference between the display brightness Bt obtained in the above-mentioned transmissive embodiment and the translucent reflector (lO
) is multiplied by the transmittance Tr based on the optical reflection loss and absorption loss caused by the addition of
When FF, Bdt=RpXT1cXTpX'ftrXB1.

On the other hand, external light is transmitted through a liquid crystal cell (3) for 1 m and a polarizer (2
), it becomes linearly polarized light, is reflected by the translucent reflector (lO), and passes through the polarizer (2) again, this time in a directly polarized state, and again enters the liquid crystal cell. (3), is reflected by the translucent mirror (6), and is reflected by the eye range (7).
leading to. Therefore, the reflectance of the translucent reflector (10) is set to Rt
r, and the LIIM intensity of outside light is Be: Then, the amount of interference caused by outside light Bdr is: Before the liquid crystal cell (3) is ON, Bdr=RsXTlc XTppXRtrXTpXBe
Or when l-1oFF', Bcir=RpXT1c XTppXRtrXTpXB
It becomes e.

Now, the brightness Bd of this embodiment, which is a hybrid transmission/reflection type, is the phase of the contribution Bdt from the light source (1) and the contribution Bdr from the external light Be, so the brightness Bd of the liquid crystal cell (3
) is ON, Bd=ReXT1cXTpX(T'trXB1+Tpp
When XRtrXBe ) OFF, Bd:zRpXTlcXTpX(TtrXB1+Tpp
XRtrXTJ-cXf3e).

Display brightness BdJ of conventional transmissive/reflective hybrid type
If I fi is expressed in the same way as above, before the liquid crystal cell is turned on, Bdj=RsXTapX'l'1cX(TpXTtrX
B1+Tpp XRtr! 'l'1cXTaXBe ) When OFF, Bdj=RpXTacXT1cX(Tp(TtrXBl
+TppXRtrXTpcXT1. cXTaXBe).

These things could be confirmed through experiments. In other words, when the liquid crystal cell of this transmissive/reflective hybrid type is turned on, the display brightness is 1/'I'ap times as much as when there is no external light, compared to the conventional transmissive/reflective hybrid type. When the brightness Be of the external light is sufficiently larger than the brightness 431 of the light source (1), it becomes brighter by a factor of Tp/(TapxTppxTa).

Normally, the polarizing plates available to us have a transmittance of 30 to 40 degrees for natural light, and a transmittance of 70 to 80 degrees for polarized light vibrating in the direction of the polarization axis. It has become clear that it is possible to achieve an improvement in brightness of about 8u.

In each of the above embodiments, the case where a TN type liquid crystal cell is used is described, but a dichroic dye is mixed into the nematic liquid crystal in the liquid crystal cell, and when an electric field is applied, the liquid crystal rotates and the dye also rotates. Even if a ()H) type liquid crystal cell is used, the same effect as in the above embodiment can be obtained. play.

In this case, it is also possible to replace the polarizing plate with a light-transmitting mirror, thereby eliminating the need for a polarizing plate at all. Alternatively, an electric field controlled birefringence type liquid crystal cell may be used. Furthermore, as long as the polarization or absorption can be controlled on a riverboat basis, a cell other than a liquid crystal cell may be used.

In addition, in each of the examples, the simplest configuration is shown, but for example, it is possible to replace the polarizer (2) with a so-called color polarizing plate that exhibits polarization characteristics only in a specific wavelength range, or to simply use a color filter. Color display can also be achieved by overlapping.

Translucent mirror (6) &''i, without being limited to those used in the above embodiments, a material such as a plastic plate, a plastic film, a glass plate, or a complex of such a Items with electric bodies such as metal, metal thin films, or metal oxides, etc.
Any material or structure can be used as long as it is transparent and selectively reflects polarized light.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a polarization control element in which the polarization state of a passing light beam changes depending on the applied voltage value, a control circuit that controls the voltage value applied to the polarization control element, and the polarization control element as described above. The display device is constructed with a translucent mirror that allows the light that has passed through the element to enter at an incident angle approximately equal to the polarization angle, and directs the reflected light to the eye range, so it can be configured so that an analyzer is not required, and parts The number of points is reduced, the device can be made cheaper, and the reliability of the device is improved.

This eliminates the absorption of light by the optical analyzer, which has the effect of greatly improving the brightness of the display.

In short, the main point of this invention is to focus on the fact that a certain 41+ translucent mirror has polarization-selective reflectivity, and to use it as an analyzer for a polarization control element that uses polarization, such as in a conventional liquid crystal display element, using a head. The point is that the translucent mirror, which is a component of the close-up display device, is replaced with polarized light selective reflection.
A higher quality display can be obtained by setting the angle of incidence of the display light on the translucent mirror to about the polarization angle.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional liquid crystal display device, Fig. 2 is a block diagram showing a transmissive head-up liquid crystal display device according to an embodiment of the present invention, and Fig. 3 is a block diagram showing a transmissive head-up liquid crystal display device according to an embodiment of the present invention. A curve diagram showing the dependence of the reflectance on the polarization ratio of the optical mirror on the incident angle. FIG. 4 is a configuration diagram showing a reflective head-up liquid crystal display device according to another embodiment of the present invention. FIG. FIG. 7 is a configuration diagram showing a transmissive/reflective hybrid head-up liquid crystal display device according to another embodiment. (3)...Polarization control element, (5)...Control circuit, (
6) Translucent mirror, (7) Eye range In the drawings, the same reference numerals indicate the same or corresponding parts. Agent: Masaru Oiwa. Procedural amendment (spontaneous f, I; a'+°j1 long palace), IG fl display f-1' petition 1977-206
No. 589 No. 2, Invention title display device 3, H to make the amendment Representative Hitoshi Katayama Part 5, Detailed explanation of the invention column 6 of the specification subject to amendment, Contents of the amendment (1) Specification, page 18 18 rows of 1-1-1”pp×R
trxBe J l−+′r,, XRt rXTec
Correct to XBe J. that's all

Claims (2)

[Claims] (1) A polarization control element that changes the polarization state of the light beam passing through it depending on the applied voltage value, a control circuit that controls the voltage value applied to this polarization control element, and a polarization control element that changes the polarization state of the light beam that passes through the polarization control element according to the polarization angle. A display device equipped with a translucent mirror that allows light to enter at an angle of incidence of , and directs the reflected light to an eye range. (2) The display device according to claim 1, wherein the polarization control element is a liquid crystal display element.